Working with an in vitro model for invasion of red cells by P. falciparum, recent work has suggested that the receptor for this malaria is part of the glycophorin A red cell complex. Various soluble substances extracted from glycophorin A are being used in blocking invasion assays. The study of the Duffy receptors for P. vivax is being reinvestigated by testing red cells of susceptible and non-susceptible primates.